1. Field of the Invention
The present invention relates generally to a method and apparatus for a communication procedure in a wireless communication system, and more particularly, to a method and apparatus for using the speed of a User Equipment (UE) or a Mobile Station (MS) for a communication procedure for selecting a cell in a wireless communication system.
2. Description of the Related Art
Recently, wireless communication systems have evolved to more miniaturize cells to support a high data rate for UEs with high mobility. Accordingly, micro cells and macro cells may coexist in the same area, and the overall system performance may significantly depend on the cell types to which the UEs are connected.
FIG. 1 illustrates a conventional wireless mobile communication system in which micro cells and a macro cell coexist. In the following description, the terms ‘cell’ and ‘Node B (or Base Station)’ will have the same meaning.
Referring to FIG. 1, a plurality of micro cells 110, 120, 130, 140, 150 and 160 are present in a macro cell 100. In the wireless communication system, however, the micro cells 110, 120, 130, 140, 150 and 160 should not necessarily be located within the macro cell 100, and may be present out of the macro cell 100.
The moving speed of a UE may be high or low within the service coverage. Reference numeral 170 represents a UE moving at low speed, while reference numeral 180 represents a UE moving at high speed.
The UE 170 moving at low speed is highly likely to be located in a micro cell represented by reference numeral 130 for a considerable time, so it is preferable that the micro cell 130, rather than the macro cell 100, is a serving cell for the UE 170. However, the UE 180 moving at high speed will be located in its current micro cell 120 for a short period of time. Due to this high speed movement, if the micro cell 120 is determined as a serving cell for the UE 180, a handover procedure may frequently occur. Thus, it would be more efficient for the macro cell 100, rather than the micro cell 120, to be a serving cell for the UE 180. In other words, the efficiency of the system may be improved by determining the cell providing a service to a UE, based on the moving speed of the UE.
In the conventional mobile communication system, a UE or a Node B estimates a channel and the speed of the UE depending on the estimated channel, and determines a target cell or serving cell to which the UE will perform handover, based on the estimated speed of the UE. However, this scheme of estimating the speed of a UE by the channel estimation tends to be inaccurate.